This paper tests the ability of two consumer theories - the theory of reasoned action and the theory of planned behavior - in predicting consumer online grocery buying intention. In addition, a comparison of the two theories is conducted. Data were collected from two web-based surveys of Danish (n=1222) and Swedish (n=1038) consumers using self-administered questionnaires. Lisrel results suggest that the theory of planned behavior (with the inclusion of a path from subjective norm to attitude) provides the best fit to the data and explains the highest proportion of variation in online grocery buying intention. Keywords Online buying intention – groceries - theory of reasoned action – theory of planned behavior – lisrel